1. Field of the Invention
This invention generally relates to a spreader attachment utilized to evenly distribute material, and specifically to a spreader attached to a farm vehicle to distribute granular and/or powdery material.
2. Discussion of the Related Art
Farmers, landscapers, and others needing to spread material over large areas need a spreading device that will allow for rapid distribution of the material being spread, covering a large area in an even spread pattern, completed in a reasonably short period of time. The spreading device often determines the success of the operation. While there have been many spreaders brought to the marketplace, the prior art spreaders do not produce a uniform distribution in a cost efficient manner. Those spreaders that do effect a uniform distribution fail to spread over a sufficiently large enough area to keep the operation within reasonable costs.
Dual disc centrifugal spreaders are well known in the art. They generally are comprised of flat discs that cast off particulate material in a horizontal plane. To achieve maximum results, these discs must maintain constant circumferential speed. The power to turn the discs generally comes from either rotating wheels contacting the ground translated through various gearing mechanisms, or power comes via a power take-off drive. While power take-off drives generally produce more constant circumferential speed, both powering methods produce irregularities in the scatter pattern over the entire scatter width, leading to overspreading of material and/or bald spots from underspreading of material, both of which cause irregular plant growth.
While higher circumferential disc speeds provide more uniform scatter patterns, they oftentimes provide too strong of an overlapping pattern in the center (behind the vehicle), laying down excess material. When the circumferential disc speed is reduced, the periphery of the scatter pattern becomes very steep outwardly, resulting in reduced spreading in the center (behind the vehicle).
Typical in the prior art, centrifugal spreaders have scoop members provided on the rotating discs for catching the ejected material and hurling this material centrifugally outward onto the ground. Both straight edge scoop members and curved scoop members having their concave side directed toward the rotating direction of the disc have been utilized to attain as broad a dispersion zone as possible by increasing the hurling distance of the material centrifugally outward of the discs.
To achieve a uniform spreading pattern, it is important for centrifugal spreaders to have the material to be spread fall upon the rotating disc within a definite area. U.S. Pat. No. 3,406,915 to Dreyer, et al. achieves this through the use of a releasable or pivotable shoot or tube underneath the opening in the hopper.
U.S. Pat. No. 3,109,657 to Dreyer is directed to a centrifugal spreader for particle fertilizer material. Material ejects out the side of a storage bin onto rotating discs having one curved scoop member and one straight scoop member. The curved member is C-shaped in cross section but maintains a constant height along the length of the member. The material feeds directly from the storage bin onto the rotating discs, the left disc, when viewed from behind, rotating clockwise and the right disc rotating counter clockwise.
U.S. Pat. No. 4,842,202 to van der Lely et al. is directed to a spreader with a hopper having two delivery parts. Distribution members are provided under the delivery parts for broadcasting material fed to them from the hopper. The distribution members are mounted on a carrier rigidly supported by and coupled to the hopper. Because the material is stored directly over the discs, a frame having significant rigidity is required.
The material feeds from the hopper directly to outlet orifices at the bottom of the hopper onto two circular discs. The discs rotate counter to one another. Each disc contains blades having a geometry that flares outward at a 15.degree. angle, including a blade visually flaring, and a blade structure directed away from the rotary axis.
What is needed, therefore, is an improved device that will provide a uniform scatter pattern and throw width, while also providing an optimal overlapping of the scatter pattern produced by multiple discs, both toward the outside or periphery of the pattern, and in the area directly behind the vehicle.